A circuit may have multiple independent grounds, that is, ground potentials that may vary with respect to each other. The grounds serve as return paths for currents (including power currents and signaling currents) flowing in a respective portions of the circuit, and may also serve as reference voltages in the respective portions of the circuit.
In such a circuit, a first ground may float with respect to a second ground, that is, a voltage difference between the first ground and the second ground may vary over time. The circuit may need to communicate information from a portion of the circuit using the first ground to a portion of the circuit using the second ground. That is, a first circuit using a first ground may need to determine a value, relative to a second ground, of a control signal generated by a second circuit using the second ground, when the first ground floats with respect to the second ground.